Mandate licensed veterinary professional supervision after surgical procedures

I’ve heard this before and thought it was madness but never thought it would come knocking at my own door our beloved dog Bella was sedated and operated on. We were told she was very ill after the surgery at 8 o clock, then at half 9 we received a call to say they found Bella dead during one of their checks. We believe she should never have been left alone not so soon after having such a procedure.